<apex:page controller="AdminPageCtrl" tabStyle="WorkTime__c">

<apex:form >
        
        Subordinates:<apex:selectList multiselect="false" value="{!selectedsubordinate}" size="1" style="width:230px">
                <apex:selectOptions value="{!optionSubordinate}"></apex:selectOptions>
              </apex:selectList>
              
        <apex:commandButton value="Show All Reports" action="{!showAllWorks}">
            <apex:param name="button1" value="Button 1" />
        </apex:commandButton>    
        
        <apex:actionStatus id="loadingStatus" startText="Please Wait. Processing..." />
        
        <apex:pageBlockButtons >
            
            <apex:commandButton value="Delete The Selected Records"/>
           
        </apex:pageBlockButtons>

        <apex:pageBlockTable value="{!relist}" var="rec" id="myTable">
  /*I want to add a checkbox, some records are selected will send to class,by the button "Delete The Selected Records"  .But I don't know how to write this code: 
           <apex:column>
                <apex:inputCheckbox >
                    <apex:param value="{!rec.Name}" name="muRecId" />  
                </apex:inputCheckbox>
            </apex:column>
  */          
            <apex:column headerValue="ID" value="{!rec.Name}" /> 
            <apex:column headerValue="LoginTime" value="{!rec.BeginTime__c}" /> 
            <apex:column headerValue="LogoutTime" value="{!rec.EndTime__c}" /> 
            <apex:column headerValue="Notes"> 
                <apex:inputText value="{!rec.Notes__c}" />
            </apex:column>
            <apex:column headerValue="Update">
                <apex:commandLink action="{!saveSingleRecord}" rerender="thePageBlock" status="loadingStatus">
                    Update
                    <apex:param value="{!rec.Notes__c}" name="myRecId" />  
                </apex:commandLink>
            </apex:column>
            <apex:column headerValue="Delete">
                <apex:commandLink action="{!deleteRecord}" rerender="myTable" status="loadingStatus">
                    Delete
                    <apex:param value="{!rec.Name}" name="deRecId" />  
                </apex:commandLink>
            </apex:column>
        </apex:pageblocktable>        
    </apex:pageBlock>
</apex:form>
</apex:page>

public with sharing class AdminPageCtrl{
    
    public List<User> userlist {get; set;}
    public List<SelectOption> optionSubordinate {get; set;}
    public String selectedsubordinate {get; set;}
    
    public List<WorkTime__C> relist {get; set;}
    
    public AdminPageCtrl(){
        relist = new List<WOrkTime__C>();
        
        
        optionSubordinate = new List<SelectOption>();
            List<User> userlist = [SELECT Name, MyPosition__c From user
                        Where MyPosition__c like 'Department%' 
                            or MyPosition__c like 'Admin%' or MyPosition__c like 'Bos%'
                        Order By MyPosition__c ASC
                       ];
            if(userlist != null && !userlist.isEmpty()){
                    for(user me : userlist){
                        optionSubordinate.add(new SelectOption(me.Name, me.Name + ' - ' + me.MyPosition__c));
                    }
            }
            
    }
    
    public pageReference showAllWorks(){
        
        relist = [select  Name, BeginTime__c, WorkerRef__r.Name, EndTime__c, Notes__c from WorkTime__c 
            where WorkerRef__r.Name = :selectedsubordinate
            Order by BeginTime__c DESC
            ];
        
        if (relist.isEmpty()) {
            ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR, 'This Employee has not ATTENDANCE INFORMATION.'));
            return null;
        }   
        return null;     
    }
    
    public void saveSingleRecord(){
        string recId = ApexPages.currentpage().getParameters().get('myRecId');
        WorkTime__c mySingleRec;
        for (WorkTime__c c : relist) {
            if (recId == c.Notes__c) {
                mySingleRec = c;
                break;
            }
        }
        if (mySingleRec != null)
            update mySingleRec;
    }
    
    public pageReference deleteRecord(){
        string recId = ApexPages.currentpage().getParameters().get('deRecId');
        for (WorkTime__c c : relist) {
            if (c.Name == recId)
                delete c;
        }
        return showAllWorks();
    }
    
}